Shock Absorbers vesus Air Bags

Ray,
These 2 items serve 2 different purposes and it is not realistic (IMHO) to ask an "either/or" type question.

The air bags will serve to enable you to maintain a better chance of keeping the bum of the truck off the ground once you hook-up the caravan.

Shock absorbers (pump-up or otherwise) are designed to "control" the action of your springs......they are not designed as a "load-bearing" component of your suspension (AFAIK).....

Cheers

Roachie

Pump Up Shokies ... Noooooooo. The role of a "Shockie" is to dampen the movement of the springs, not to carry load.

In the first place visit a good 4x4 suspension specalist to ensure your current suspension is in good order. Depending on the age of the vehicle you may need to replace some or all of your existing suspension components.

You can then look at what rear spring rating you want to run in the rear of the vehicle for the load you are carrying. You may decide to go for a heavier rate rear spring that will enable you to safely tow with nothing else. Otherwise you can go for a softer spring, but add a air bag such as a polyair, that can be inflated to compensate for the extra weight for the van when you are towing.

Ray,

Shocks were never designed to take the weight of the vehicle. They are designed to keep the wheels on the ground.

Springs with the aid of air bags will support the weight of the vehicle.

Go with the air bags.

Wayne

Ray
My troppy might drop 1" inch when I sit the 20ft van on the towbar. No air bags , eventually they will let you down by stone abrasion or holed. even Semi-trailers and Prime movers with air bags get let down now and then , although I loved the airbags on the drive axles of the semi because that meant not having to wind the trailer legs down hard, just down until they touched ground and a couple more turns then let the air out of the bags , made life a lot easier .So the best investment you could get is a Spring upgrade , Mine is ARB ,
And of course others have you the info about Dampers.

Used to run a pair of Munroe pump ups on the back of my panel van (god that was a while ago!) Worked great. Just like having a set of polyairs but polyairs weren't around in those days.
For serious use on a 4B I'd go a good set of shockies with polyairs. This will keep the load where it should be, on the spring seats, not the shockie towers.

One thing that is often overlooked when fitting stiffer or pump up shocks is the strength of the mounting points. I will always remember a customer at work many years ago who bought a new Toyota station wagon then fitted stiffer shocks all round. He returned six months later with the top mounts at the rear ripped right out of the floor and expected the damage to be repaired under warranty. The mounts were not designed for the increased pressure applied by his aftermarket shocks so the floor surrounding them flexed excessively and eventually work hardened and cracked. There is no way in the world the standard shocks would have done that.

When thinking about different springs, many people don't realise they are measured in both "load" and "rate". Load concerns the height at which they will support a given weight. Rate is the amount a given weight will compress them one inch. For example 200 pounds may compress a spring one inch, 400 pounds will compress it two inches, 600 pounds three inches and so on.

A coil spring with many turns of thin wire can hold your car at the right height so you could say the "load" is correct but it could bottom out when you sit on the tailgate so the "rate" is too low. A spring with only a few turns of very heavy wire could also hold the car at the right height but may hardly deflect at all when you fill the car with bags of cement so the rate is too high.

All of this can be calculated mathmatically by spring makers when designing new springs providing they know the unsprung weight of each end of the car and what type of ride the owner wants.

This is just something to keep in mind when discussing replacement non original springs for your car.

Brian

I fitted Monroe Pump-up shock absorbers to my Nissan Patrol in 1972, but they always leaked out all air within a week.

Based on the replies here, it seems that these aren't available any more and people have no idea how they work.